1. Field of the Invention
This invention relates generally to All Terrain and Mountain Bicycles and to a means for softening the ride over rough ground without sacrificing pedaling effeciency.
2. Description of the Prior Art
The only shock absorbtion feature of the most widely used ATBs is that provided by oversize tires and the flexibility of the front forks. One model in limited production adds flexibility to the frame to soften the ride by replacing the down tube with one or two steel cables which terminate in compression springs under the bottom bracket, and adding a kevlar flexure at the joint between the top tube and the seat tube to allow the frame to flex without breaking. Another model uses a Hannebrink rear suspension which transfers load on the rear wheel to the frame through a shock strut and pivot for the chain stays, and which allows the rear wheel to bounce with minimum disturbance to the frame. The cable/spring arrangement provides a slight softening of the ride coupled with a modest reduction in pedaling efficiency, while the Hannebrink system provides major shock absorbtion with a considerable reduction in both traction and pedaling efficiency. Adding flexibility anywhere along the load path between the handlebars, bottom bracket and rear wheel detracts from pedaling efficiency because the loads imposed by pedaling flex the structure, which absorbs energy and reduces the portion of pedal power delivered to the rear wheel. Therefore, the only way to soften the ride of ATBs without sacrificing pedaling efficiency is to add shock absorbtion to the front fork, while maintaining the frame, handlebars to rear wheel, as stiff as possible.